In recent years, the following white light emitting device has attracted attention as a white light emitting device that has long life and low power consumption. The white light emitting device is adapted to obtain white light as a composite spectrum, which is generated by additive color mixing of light obtained from a semiconductor light emitting element and a phosphor, by combining the semiconductor light emitting element, such as a laser diode (LD) or a light-emitting diode (LED) emitting blue light, with the phosphor using the semiconductor light emitting element as an excitation light source. It has been expected that the white light emitting device is used as a white light source of a vehicle lamp, particularly, a vehicle headlamp (see Patent Document 1).
Here, in accordance with chromaticity regulations, it is required that an emission spectrum of the white light source of the vehicle lamp is in a range of a predetermined chromaticity coordinates (cx,cy). For example, according to JIS:D5500, it is required that the emission spectrum of the white light source is in the range of an area A shown in a chromaticity diagram of FIG. 6.
Meanwhile, the area A is represented by the following expressions.
<Chromaticity Regulations (JIS: D5500) of White Light Source of Vehicle Headlamp>Yellow color direction cx≦0.50Blue color direction cx≧0.31Green color direction cy≦0.44 and cy≦0.15+0.64cx Violet color direction cy≧0.05+0.75cx and cy≧0.382
As an example of a white light emitting device that can emit white light corresponding to the chromaticity regulations at high emission intensity, there is known a light emitting device that emits white light by combining an InGaN-based semiconductor light emitting element having a peak emission wavelength in a blue wavelength range (420 to 490 nm) and a cerium-activated yttrium-aluminum-garnet (YAG)-based yellow light emitting phosphor having a peak emission wavelength in the range of 510 to 600 nm (see Patent Document 2).    Patent Document 1: JP-A-2004-095480    Patent Document 2: Japanese Patent No. 3503139